This invention concerns tools used to remove a volume of material from a workpiece and is especially concerned with the use of center cutting end mills for forming contours in titanium materials.
Materials such as titanium have relatively light weight and great strength and, for that reason, are used in structural and operating parts for aircraft. Structural parts for aircraft, when made from titanium, must be thin in cross section while having flanges perpendicular to said cross sections. In order to manufacture such parts having thin cross sections from titanium, it is necessary to machine said parts out of solid blocks of stock. This usually requires that more titanium material be removed from the block than will remain in the workpiece.
To date, the method used in removing the titanium has been using a drill to make a cylindrical access hole with a predetermined depth in the pocket to be formed in the titanium. End mills are then lowered to a fraction of the depth of the access hole and traversed over an x and y axis until the entire surface of the pocket to be formed is traversed. The method is again repeated until each fraction of depth of cut totals the required part print depth.
The problem with the above procedure is that it is extremely time consuming, and the cutting edges of the end mills are easily and very often damaged. The cause of the damage usually is due to the cutting edge recutting an already machined chip.
When the cutting edge of the end mill encounters a previously machined chip, it can cause systems deflection and damage itself. When utilizing carbide instead of H.S.S. material in the drill or end mill, the carbide cutting edge can also be damaged when a previously machined chip is caught between the cutting edge and the uncut material.